1. Field of the Invention
This invention relates to a bicycle speed change lever assembly, and more particularly to improvements in the lever assembly for operating a derailleur to shift a drive chain from one to another of diametrically different sprockets of a multiple freewheel or multiple chainwheel. More specifically, the invention is directed to a bicycle speed change lever of the type that is capable of selectively providing two operational modes.
2. Prior Art
As is well known, bicycles are equipped in many cases with a speed change mechanism to enable cycling suited to a particular road condition or to a cyclist's desire. Such speed change mechanism includes for example a rear derailleur of the type that comprises a shiftable cage rotatably supporting a pair of guide pulleys and a control mechanism such as a parallelogrammic linkage mechanism for displacing the guide pulleys laterally of a multiple freewheel to shift a drive chain engaging with the pulleys from one sprocket to another of the freewheel. The speed change mechanism may further comprise a pair of parallel guide plates and a control mechanism such as a parallelogrammic linkage mechanism, similar to that of the rear derailleur, for displacing the guide plates laterally of a multiple chainwheel to shift the drive chain from one sprocket to another of the chainwheel.
The movement of the guide pulleys or the guide plates is controlled by a control lever which is operatively connected to the parallelogrammic linkage mechanism via a control cable a part of which extends along a cable winding groove formed in an outer circumference of a cylindrical boss portion of the control lever which has a handle portion extending radially from the boss portion. The control lever is pivotally mounted at the boss portion to a suitable part of a bicycle frame. When the control lever is pivoted, the cable is wound up along the winding groove onto the boss portion or paid out therefrom to vary a tension of the cable thereby to regulate the parallelogrammic linkage so that it is correspondingly deformed to bring the guide pulleys or the guide plates to a lateral position predetermined by the pivotal position of the control lever.
Normally, the control lever is pivoted steplessly. It is, thus, quite difficult for an unskillful cyclist to so operate the control lever as to bring the guide pulleys or the guide plates to an optimum position relative to each sprocket of the multiple freewheel or the multiple chainwheel. As such, the guide pulleys or the guide plates are sometimes stopped erroneously at a position intermediate two adjacent sprockets, failing to effect intended shifting of the drive chain onto a selected sprocket of the multiple freewheel or the multiple chainwheel. This gives rise to objectionable gear noises or unwanted vibration of the drive chain.
In order to improve the maneuverability of the control lever, it has been proposed to incorporate into the lever assembly a click mechanism which serves to clickingly hold the control lever at each of predetermined pivotal positions. With the use of the click mechanism, any cyclist, skilled or unskilled, can easily operate the control lever to bring the guide pulleys or the guide plates accurately to an optimum position immediately under a selected sprocket of the multiple freewheel or the multiple chainwheel and thereby conduct desired speed change.
However, the proposed clicking type lever assembly is not always advantageous and can sometimes become troublesome for example when the length of the control cable spanning between the control lever and the derailleur unexpectedly increases because such an increase causes a positional deviation of the guide pulleys or the guide plates from an intended gear position corresponding to each clicked pivotal position of the control lever. Although the positional deviation of the guide pulleys or the guide plates can be corrected by readjusting the cable length, such length readjustment requires considerable time and skill.
Japanese Patent Application Laid-open No. 60-209377 (Application No. 59-67163 filed Apr. 3, 1984, Inventor: Masashi Nagano) discloses a bicycle speed change lever assembly which has overcome the above described disadvantage of the conventional clicking type lever assembly. More specifically, the lever assembly of this Laid-open Application comprises a control lever rotatably mounted on a fixed support shaft, a click ring mounted to the control lever for co-rotation therewith and axially divided into a non-clicking zone having a smooth inner contact surface and a clicking zone formed with a pair of diametrically opposite arcuate rows of clicking holes in identical arrangement, a cap non-rotatably mounted on the support shaft, an elastic C-ring retainer non-rotatably but axially slidably mounted on the cap within the click ring and rotatably holding a pair of steel balls in abutment with the click ring, and a mode selector for axially moving the retainer relative to the click ring.
In operation of the lever assembly with the balls positioned in the clicking zone of the click ring, the control lever can be clickingly pivoted on the support shaft by the successive engagement of the balls into the respective clicking holes of the click ring.
In addition to such a clicking operational mode, the mode selector may be operated to displace the balls into abutment with the smooth contact surface of the click ring in the non-clicking zone thereof, whereby the control lever can be pivoted steplessly. During this non-clicking operational mode, the cap is clamped by a bolt to press a friction disc into frictional engagement with the control lever, so that the lever can be frictionally held at any pivotal position despite a tension applied through a control cable.
However, the lever assembly of Japan No. 60-209377 has a drawback that the click ring is liable to damage during the non-clicking operational mode due to contact of the balls with the click ring under the biasing force of the C-ring retainer. In fact, the C-ring retainer is diametrically contracted during the non-clicking operational mode to increase the biasing force thereof, making the problem more serious.
Japanese Patent Application Laid-open No. 61-33380 also discloses a speed change lever assembly which enables two operational modes, i.e., clicking and non-clicking modes. More particularly, the lever assembly of this Laid-open Application comprises a click member having a cylindrical body non-rotatably fitted on a fixed support shaft and an annular end flange formed on one side surface thereof with a pair of diametrically opposite sets of clicking serrations in identical arrangement. A control lever is rotatably mounted on the cylindrical body of the click member. An engaging ring co-rotatable with the control lever is slidably fitted on the cylindrical body of the click member in facing relation to the annular end flange of the click member and has a pair of diametrically opposite engaging ridges. A spring urges the engaging ring toward the annular flange of the click member, so that the engaging ridges of the ring come into selective engagement with the clicking serrations in the respective sets. A pair of pusher pins movably penetrate through the annular end flange of the click member for sliding abutment with the engaging ring. A rotationally operable mode selector incorporating a cam means operates the pusher pins to move the engaging ring toward and away from the annular end flange of the click member.
When the engaging ring is close to the annular end flange of the click member with the ridges engaging with the clicking serrations, the control lever can be clickingly pivoted on the support shaft. On the other hand, when the engaging ring is moved away from the annular end flange against the urging force of the spring by means of the mode selector through the pusher pins, the engaging ridges disengage from the clicking serrations to enable stepless pivotal movement of the control lever.
The lever assembly of Japan No. 61-33380, however, has a disadvantage similar to that of Japan No. 60-209377 since during the non-clicking operational mode the engaging ring is kept in sliding contact with the pusher pins under the increased urging force of the compressed spring.
It is, therefore, an object of the present invention to provide a speed change lever assembly which, while ensuring selection between a clicking operational mode and a non-clicking operational mode, permits elimination of the above discussed drawbacks to achieve a longer service life.
Another object of the invention is to provide a bicycle speed change lever assembly which has two or more kinds of clicking operational modes in addition to the non-clicking operational mode.
According to the present invention, there is provided a bicycle speed change lever assembly comprising a support shaft fixed to a bicycle frame; a control lever having a hollow boss portion rotatable about the support shaft and having a handle portion integral with and extending from the boss portion, an annular internal space being formed in the boss portion; a click ring accommodated in the internal space and co-rotatable with the boss portion, the click ring being provided on one side surface thereof with at least one arcuate row of clicking recesses; a retainer disposed in juxtaposition to the click ring in facing relation to the one side surface of the click ring and non-rotatable relative to the support shaft; at least one steel ball loosely retained by the retainer in corresponding relation to the row of clicking recesses and having a diameter larger than the wall thickness of the retainer; elastic means for urging the click ring toward the retainer; a mode selector disposed in juxtaposition to the retainer so that the retainer is interposed between the mode selector and the click ring, the mode selector being provided on one side thereof facing the retainer with at least one backup portion and at least one shelter recess, the mode selector being angularly adjustable to take a selected one of angular positions which include a backup position in which the backup portion forces the ball into abutment with the one side surface of the click ring and a non-backup position in which the ball is allowed to retreat into the shelter recess; and means for locking the mode selector at the selected one of angular positions.
Other objects, features and advantages of the present invention will become apparent from the description of preferred embodiments given with reference to the accompanying drawings.